Rough Unstable Idle

The engine runs unevenly. In severe cases, the car may actually shake. The engine idle may hunt or fluctuate in rpm and may be bad enough to stall.

POSSIBLE CAUSE ACTION

AT ALL TIMES
EGR malfunction Check EGR system in "Testing
Flange gasket leaking Procedures" in Emissions
valve open (valve should
be closed at idle)



Air management valve Check Air Injection system in
malfunctioning, no "Testing Procedures" in Emissions
air to ports while
in closed loop



PCV valve malfunctio Check PCV system in "Testing
Procedures" in Emissions



AT OPERATING TEMPERATURE
Faulty canister purge Check Evaporative system in
and bowl vent valve "Testing Procedures" in Emissions



Restricted exhaust system Check Catalytic Converter system in
"Testing Procedure" in Emissions



Idle speed too low Check idle load compensator devices
in "Testing Procedures" and idle speed
in "Adjustment Procedure" in Emissions